A two-stroke engine of the above kind is disclosed in U.S. Pat. No. 4,248,185. A carburetor is arranged in the intake portion of the mixture overflow channel which enriches through-flowing fresh air with fuel to form an air/fuel-mixture. The mixture is admitted into the cylinder combustion chamber after a component quantity of fresh or scavenging air has been admitted.
The preparation of the mixture by means of a carburetor is not always satisfactory especially with respect to the quality of the exhaust gas. It has therefore already been suggested to inject fuel as an adapted quantity by means of a pneumatically operated injection pump as disclosed in U.S. Pat. No. 4,700,668. However, problems develop with respect to the preparation of the mixture when fuel is injected especially for fast-running two-stroke engines. Only precision machined and therefore expensive injection nozzles distribute the fuel within the short injection time to an extent fine enough that a good mixture formation is assured by the vaporization of the fuel. A high injection pressure is also needed to permit the fuel to exit from the injection nozzle finely distributed as a fuel mist.